Hydraulic telescoping shock absorbers are comprised of precision tubes, rods, valves, seals and bearing elements filled with hydraulic oil. The piston valve, and more specifically, the valve body, separates the valve into a rebound side and a compression side and controls the rebound and compression flow of the oil to provide controlled damping. A seal element or seal around the valve body is designed to minimize or eliminate oil bypassing the valve body which affects the performance of the shock absorber. The force developed by the pressure drop of the oil across the piston valve is transmitted by the piston rod to a vehicle body to which the shock absorber is attached.
The piston valve (also known as the “cage valve”) is unique to all other damping valves in that the seal element, housed between a floating retainer 10 and floating disc 11, moves relative to the valve body 12 by hydraulic pressure in the damper compression direction against a spring 13 to control compression damping forces. FIG. 1 shows the valve in the closed position and FIGS. 1A and 4 show the valve in the open position. In particular, the floating disc 11 identified in the drawings is shown in the closed and opened positions, respectively allowing a different flow path through the valve body 12. The compression and rebound flow patterns are identified in FIGS. 1, 1A and 4.
The piston valve or cage valve is also unique in that it enables oil flow from the center of the piston valve to the end of the piston rod 14 by being threaded directly to the end of the piston rod without an additional fastener, i.e. nut, bolt, screw, etc. secured to the piston rod.
The prior art seal element 15 design shown in FIGS. 1, 1A and 2 has a round cross-section with a single small contact surface area against the cylinder wall 16. This small contact area does not provide an adequate seal with the cylinder wall and over time deteriorates, resulting in insufficient sealing ability and pressure leakage which negatively affects the performance of the shock absorber. Additionally, the round cross-section seal element 15 deforms into an oblong cross-section during compression of the seal element, resulting in a single contact point with the cylinder wall 16. Repeated reciprocal movement of the seal element 15 in the cylinder causes the portion of the seal element at the single contact point to rub against the cylinder wall 16 and wear out prematurely. As the seal element 15 wears, the seal formed between the seal element and the cylinder wall 16, i.e., the effectiveness of the seal, decreases thereby reducing the function and effectiveness of the shock absorber cross-section.